Secondary batteries are now employed in various products such as cell phones, personal computers, power tools, and hybrid electric vehicles (HEVs), and for these applications, an alkaline storage battery is used. Such an alkaline storage battery uses, as a negative electrode active material, a hydrogen storage alloy having an aluminum (Al)-containing composition that achieves excellent stability in the crystal structure even after repeated charging and discharging cycles.
A nickel positive electrode typically uses nickel hydroxide (Ni(OH)2) as a main component of the positive electrode active material. To meet the recent demand for much higher capacity, for example, Patent Document 1 (JP-A-10-172561) has disclosed adding aluminum (Al) to nickel hydroxide (Ni(OH)2).